I've made it!
As suggested from Jao modtool is very useful to extract audio sfx....my procedure is the following:
first open sfx_inside.iff with the
modtool just to decompress the file...and locate the sfx slot you want to replace
1. Extract the desired sound as orig.n2kf click on export file
2. Edit/Replace with Audacity....it MUST BE OF THE SAME LENGHT OF THE ORIGINAL! And you must import it as RAW file
3. Export the file as RAW new.n2kf
now it comes the tricky part...
4. Open sfx_inside.iff (decompressed before) with a Hex Editor Like Edit Pad Pro
5. Open orig.n2kf in the editor also
6. Open new.n2kf in the editor also
7. Search into sfx_inside.iff all the orig.n2kf (omit those first hex bytes 010000000500000001000000DC010100
44AC000000000000B8030200000000000000000000000000 )...you'll get the correct offset inside the file.....
8. Replace the bytes of new.n2kf into sfx_inside.iff starting from the just found offset + omitted bytes
9. Save and...voila! The new sound will be imported into the game ^__^ on the correct slot
Sorry...I wrote this in just few minutes...I promise a in-depth tutorial as I get more time...
I just tested importing a StreetBall rim sounds into sfx_inside.iff ^_^...hopefully someone can write a tools to automate this ......I'll import some sfx and then post the sfx_inside.iff here later....